CODEWITHSUNDEEP
linuxunix
udi
udi

Reputation: 508

Difference between nproc and ulimit?

Ulimit and nproc are both used for limiting the system processes and resources for a particular user or application (correct me if I am wrong) in *nix system. What is the major difference between the two?

Upvotes: 14

Views: 58891

Answers (2)

Lev Levitsky
Lev Levitsky

Reputation: 65791

There are two different instances of nproc.

nproc from coreutils prints the number of processors. From man nproc:

NPROC(1)                         User Commands                        NPROC(1)

NAME
       nproc - print the number of processing units available

SYNOPSIS
       nproc [OPTION]...

DESCRIPTION
       Print  the number of processing units available to the current process,
       which may be less than the number of online processors

However, the nproc setting in /etc/security/limits.conf indeed limits the number of processes:

From man limits.conf:

       nproc
           maximum number of processes

Upvotes: 20

P.P
P.P

Reputation: 121387

 both are used for limiting the system processes and resources

If you are referring to the nproc parameter in limits.conf then yes it's for limiting the number of processes.

The shell utility ulimit is used for getting/setting resources' limits, too. For example, getting the stack size for each process:

$ulimit -s

Changing the stack size to 1MB:

$ulimit -s 1024

Changing the stack size to unlimited:

$ulimit -s unlimited

There's no difference between setting/changing resources via /etc/security/limits.conf`` andulimit`.

However, the shell utility ulimit changes are only applicable to the current shell. But /etc/security/limits.conf changes will be applicable system-wide for all the specified users. Besides /etc/security/limits.conf typically can be changed only by a privileged users.

But ulimit doesn't require privileges.

So you can think of ulimit as for temporary changes to resource limits just for you, which you can change yourself; whereas /etc/security/limits.conf is for system-wide setting (for one or more users) which you can't usually change (typically your system administrators sets resource limits, if any).

Whereas nproc(1) utliity is totally different which just lists the available number of processors.

Upvotes: 4

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